We propose investigations in 2 major areas aimed ultimately at elucidating a potential hormone-related role for Ureaplasma pathogenicity in humans: (1) Fundamental biology of ureaplasmas, including (a) a systematic study of Ureaplasma cell and colonial morphology, (b) the effect of ammonia and CO2 on Ureaplasma growth and urease activity, (c) enzyme localization in ureaplasmas - urease, ATPase, NADH oxidase, and (d) further characterization of the Ureaplasma urease activity in a simple cell free assay system. We are also investigating the effect of medium tonicity and urea toxicity on Ureaplasma growth. (2) Ureaplasma-cell interaction in vitro. Our previous results indicate that ureaplasmas interact with cells in culture and cause a discernable cytotoxic effect although the interaction (and cytotoxic effect) is not maintained after subcultivation. We found that pretreatment of the ureaplasmas with proteolytic enzymes results in a more persistent interaction between ureaplasmas and eukaryotic host cells in vitro. This work will be pursued in terms of models for both mycoplasma-cell interactions and fusions (or the lack of them) between different cell types.